title: Daptomycin non-susceptibility in vancomycin-intermediate Staphylococcus aureus (VISA) and heterogeneous-VISA (hVISA): implications for therapy after vancomycin treatment failure.
abstract: OBJECTIVE
  The aim of this study was to establish the relationship between reduced vancomycin and daptomycin susceptibility among Australasian vancomycin-intermediate Staphylococcus aureus (VISA) and heterogeneous-VISA (hVISA) isolates from patients never exposed to daptomycin.
  
  
  METHODS
  Forty-seven stored clinical isolates of hVISA/VISA collected before November 2008 from around Australia and New Zealand were selected. Daptomycin and vancomycin MIC testing was performed using broth microdilution (BMD) and Etest methods. Daptomycin population analysis was performed on a subset of isolates.
  
  
  RESULTS
  The percentage of daptomycin non-susceptible isolates was 0% for vancomycin-susceptible S. aureus (VSSA) (Etest and BMD), for hVISA it was 26% by Etest and 15% by BMD, and for VISA 62% by Etest and 38% by BMD. Population analysis profile testing demonstrated daptomycin heteroresistance among the hVISA and VISA strains tested.
  
  
  CONCLUSIONS
  This is the highest rate of daptomycin non-susceptibility reported among hVISA isolates to date. Clinicians should exhibit caution when using daptomycin in situations where serious hVISA or VISA infection is a possibility.
authors.affiliation: Department of Microbiology, Austin Health, Heidelberg, Victoria, Australia.
authors.forename: Peter G
authors.initials: PG
authors.lastname: Kelley
authors.forename: Wei
authors.initials: W
authors.lastname: Gao
authors.forename: Peter B
authors.initials: PB
authors.lastname: Ward
authors.forename: Benjamin P
authors.initials: BP
authors.lastname: Howden
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology* / Q000627:therapeutic use; D001315:Australia; D017576:Daptomycin / Q000494:pharmacology* / Q000627:therapeutic use; D024881:Drug Resistance, Bacterial; D006801:Humans; D008826:Microbial Sensitivity Tests; D009520:New Zealand; D013203:Staphylococcal Infections / Q000188:drug therapy / Q000382:microbiology; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000302:isolation & purification; D017211:Treatment Failure; D014640:Vancomycin / Q000494:pharmacology* / Q000627:therapeutic use
chemical_list: D000900:Anti-Bacterial Agents; D014640:Vancomycin; D017576:Daptomycin